Introduction With the development of the national economy, the scale and structure of power systems are becoming increasingly larger and more complex, and the daily management of relay protection is also becoming increasingly complex. For regional power supply companies, their power grids span multiple voltage levels, from 110 kV to 10 kV. This paper proposes a multi-voltage level relay protection setting and information management system that integrates Web technology, enabling setting and coordination for multi-voltage level power grids, and realizing protection setting for multi-voltage level power grids. Furthermore, with the widespread application of Internet/Intranet technology within the power system, more and more applications are developing towards the Web. This system, integrating Web technology, realizes networked management of parameters and setting information, improving the efficiency of management work. 1 System Overall Design The multi-voltage level power grid relay protection setting and information management system that integrates Web technology is a relatively complete application system for regional power supply companies. It adopts a browser/server (B/S) model. The entire system is installed on a server, where administrators use various functions, and network users query parameter and setting information in the database through the Web server. The system development adopts a component integration design pattern, based on a front-end graphical interface and a back-end database, connecting various functional components according to a component-attached method. Administrators trigger all functions through a graphical interface, and each functional component reads and stores data from the database through the database component. Network users perform limited read operations on the database through the web server component and the database component. This approach facilitates user access to all system functions while ensuring data security and accuracy. It also facilitates further improvements to system functions by developers and makes debugging and unified management of each component easier. The overall system structure is shown in Figure 1. It mainly consists of the following parts: 1) Graphical Interface Component. This component is the interface between the system and the user. It is an object-oriented power grid drawing tool that provides functions such as drawing, cutting, pasting, copying, moving, rotating, scaling, color changing, and eagle-eye effects for various graphic elements. This allows users to easily and quickly draw clear, aesthetically pleasing, logically laid out, and correctly topologically analyzed network diagrams, supporting full-screen dynamic scaling and screen roaming. 2) Parameter Management Component. This component reads and stores various parameter data such as graphic element information, component parameters, and setting information in the network diagram. It can also complete the input and output of equipment and parameter information, providing functions such as browsing, searching, printing, and categorized retrieval. 3) Short-circuit current calculation component. This component can simulate various possible fault types and fault points to calculate short-circuit current. It can calculate the short-circuit current values ​​for three-phase short circuits, two-phase short circuits, single-phase ground faults, and two-phase ground faults under various power grid modes (large-scale, small-scale, and maintenance/inspection). It can also store the calculation results and display and print them in tabular form. 4) Setting calculation component. This component calculates the setting values ​​of switches and components based on the calculated short-circuit current and protection configuration according to the corresponding setting principles. It can also save and modify the settings according to user selection. This component adopts an adaptive setting method. Regarding protection setting principles, the system first analyzes the operating status of each line through network diagram analysis, and then recommends settings to the user based on the corresponding protection setting principles, making the system initially intelligent. Regarding protection verification, after protection setting is completed, the system can verify the existing protection settings based on other operating modes and maintenance operating modes set by the user. Based on the verified sensitivity, it solicits user opinions and either re-sets or maintains the original settings. 5) Notification Form Component. This component allows for the configuration and setting value management of relay protection for switches and components, storing relevant parameters in the notification form database. It also enables the automatic generation of setting calculation sheets and flexible notification form management to complete the final review and execution process. 6) Multi-level Power Grid Management Component. For local power supply companies with multi-level power grids, this component divides the entire power grid into interconnected multi-level network diagrams. It handles the interrelationships between these multi-level network diagrams, enabling functions such as short-circuit calculations and coordination of protection settings and timing between multi-level power grids. 7) Web Information Management Component. This component is the backend management program for web information publishing and online users. Administrators use this component to control the types and content of data published on the web, add and delete network user accounts, and set user access permissions. 8) Web Server Component. This component is the interface between the server database and network users. It provides network users with login, logout, and browsing, querying, and categorized retrieval functions for parameters and settings. 9) Database Component. This is the foundation of the entire system, storing all parameters and settings used by the system. Its ODBC interface provides the system with reading and storage services for parameters and setpoints; the ADO interface connects to the Web server component, providing it with database query services. 2. System Development and Features The system development process consistently employs software engineering methodologies, standardizing the requirements analysis, overall design, detailed design, coding, and testing processes. This ensures the entire system is functionally complete, structurally clear, and component-independent, improving program quality and development efficiency. Object-oriented analysis (OOA) is used in the requirements analysis and overall design phases, utilizing the standard modeling language UML to construct the system model. The system development process employs a component integration approach, improving code maintainability and reusability. Object-oriented programming (OOP) is used in the coding process, employing Microsoft Visual C++ 6.0 as the programming tool, making the program compatible with Windows 9X/2000/XP operating platforms. The program extensively utilizes dynamic memory allocation and reclamation techniques, exception handling mechanisms, and multithreading techniques, giving the system excellent compatibility, high reliability, and strong flexibility. Meanwhile, due to the component-integrated design approach, the internal data and operations of each functional component exhibit high cohesion, while the components themselves are loosely coupled, with data exchange occurring through component interfaces. This component-based approach gives the entire system strong scalability, allowing for the addition or removal of functional components to meet diverse user needs. The system uses a graphical user interface (GUI) as its front end, serving as the interface between the user and the system. Various system functions can be performed within the GUI. The component library within the GUI defines a variety of electrical components, enabling users to easily draw clear, aesthetically pleasing, and accurate power grid diagrams. After each component is drawn, a pop-up dialog box allows the user to input relevant parameters, organically combining network diagram drawing with parameter input. The system also provides functions such as automatic component positioning, parameter modification, network diagram zooming, and navigation for user convenience. The GUI incorporates numerous user-friendly design features; users can click on corresponding menu items or directly click on components in the network diagram to query, modify, and delete equipment parameters, perform short-circuit current calculations, and manage relay protection settings and values ​​for switches or components. Considering practical user issues, error prevention and handling mechanisms were incorporated into the interface design, improving the system's error correction and fault tolerance capabilities. Abundant explanations and prompts effectively prevent user misoperations, significantly increasing system stability and reliability. For more complex operations, wizard pages were designed to guide users through the process. The interface also provides excellent help functionality, resolving user questions in real time, making the software easy to learn and use. The backend database component is the foundation and core of the entire system. This component has two interfaces serving the system: a standard ODBC interface, which connects the main program to the database; and an ADO interface, which connects the web component to the database. Both of these are commonly used general-purpose database interfaces, allowing the system to be easily ported to different databases and upgraded relatively easily to utilize large databases such as SQL and Oracle to adapt to different application needs. The database used in this system is a comprehensive database of various power grid parameters and settings, reflecting not only the data content itself but also the relationships between data points. The database adopts a relational structure and employs database design paradigms for standardization, maintaining data integrity and consistency, and reducing data redundancy. The database tables are mainly divided into three categories: element information tables, component parameter tables, and relay protection configuration and setting tables. Various technologies are used in the database implementation to improve security, data integrity, and query speed, such as creating indexes and keys for tables; defining relationships between related fields in tables; and implementing concurrency control, security checks, and constraints to prevent breaches of integrity for database access. In summary, the database has a good structure, is secure and reliable, and highly efficient, fully meeting the system's requirements. Each functional component is the core of the entire system. All system functions use the database as their data source and are implemented through a graphical interface. The graphical interface calls each functional component, retrieves the required data from the database, performs corresponding operations according to user requirements, and then saves the results in the database. Each functional component is independent, and the data exchange mainly relies on the database. This independent structure facilitates system modification and expansion. 3. Implementation of Multi-Level Power Grid Management Functions For regional power companies, the voltage levels of their power grids typically range from 110 kV to 10 kV, spanning multiple voltage levels. Their protection setting tasks also cover switches and equipment at these voltage levels. However, current setting systems are mostly designed for a fixed voltage level power grid, resulting in poor applicability. To address this issue, this system has developed a multi-level power grid management function. This functional component links the previously independent power grid diagrams at different voltage levels, forming a complete network structure. The component's function consists of three parts: first, network diagram association settings; second, network diagram association operations in short-circuit current calculations; and third, network diagram association operations in protection settings. The network diagram association settings primarily allow users to configure the association relationships between corresponding buses in different network diagrams. For multi-voltage level power grids, the grid can be divided into several smaller grids according to voltage levels. The most important of these is the main grid, which is generally the highest voltage level grid. It is the core of the entire power grid, connecting the lower voltage level grids. Before setting up network diagram associations, a main network diagram is first drawn based on the main grid structure, and the main buses of the low-voltage level grid are drawn in this main network diagram. The main buses of the low-voltage level grid are often the medium and low voltage buses of the transformers in the main grid structure. Then, the network diagram at the next lower voltage level, i.e., the sub-network diagram, is drawn. After the network diagrams are drawn, the association function of the multi-level grid management component is used to select the buses in different network diagrams for corresponding association settings. The network diagram association operation in short-circuit current calculation is the process of equivalent association between different network diagrams during short-circuit current calculation. During short-circuit current calculation, the program first performs a depth traversal of the network diagram based on the user-preset association information to calculate the equivalent impedance on the associated buses, then backtracks to the upper-level network diagram and modifies the equivalent impedance on the corresponding buses. By traversing and calculating the equivalent impedance on all associated buses, the short-circuit current calculation of the current network diagram is then performed. This ensures that the short-circuit current calculation in different network diagrams takes into account the operation of the entire network, making the results more accurate. Because it employs a traversal and backtracking method, it supports multi-level power grids without limitations on the number of levels. The network diagram association operation in protection setting is the process of associating protection settings with time. When setting switch and component protection, if the switch or component that the user selects to coordinate with exceeds the scope of this network diagram, the component will adaptively search in relevant network diagrams according to the user-defined association relationships, find the switch or component to be coordinated, and extract its settings for the protection settings and time calculations in the current network diagram, thereby ensuring that the protection settings and time of the entire power grid are coordinated. The association relationships between multi-level power grid network diagrams are stored in a database by the component, allowing users to easily query, add, modify, and delete them without changing the content of the network diagram, ensuring safety and convenience. 4. Implementation of Web Functions Currently, the network construction within power systems is becoming increasingly mature, and more applications will gradually shift to networks. To meet the needs of network users, this system has developed network functions. Considering that the main purpose of network users using the network functions of this system is for simple functions such as data query, the system adopts a browser/server (B/S) model. The B/S (Browser/Server) model eliminates the need for client software development, facilitating management and maintenance, offering high development efficiency, short development cycles, and platform independence. It is particularly suitable for information management systems primarily focused on information retrieval. Network users access the server via web browsers to perform queries and other operations. These service requests are transmitted to the server via data packets, captured, interpreted, and executed by ASP components, which then access the database through ADO objects and return the corresponding data, also transmitted back to the user's browser in data packets for display. To handle server-side script commands, a server with a scripting engine is required, such as IIS (Internet Information Server) running on NT or Win2000, or PWS (Personal Web Server) running on Win98. As a service system for the protection department, this system should be installed and run on the protection department's server within the power company's local area network, providing network services to the entire power bureau. Internet users can also access the system's webpage through a browser after logging into the power bureau's dedicated network. The system's network functionality is primarily implemented by three components: a Web information management component, a Web server component, and a database component. The Web information management component serves as the management backend for the Web service. Administrators can use this component to add and delete network user accounts, set user query permissions, configure accessible device parameters and protection settings via the Web, and create downloadable protection setting notifications. All these settings are stored in the database. The database component is the core of the Web service, providing data support. It processes and responds to data requests from the Web server component. The Web service component is the main body of the entire Web service, through which network users access the backend database to obtain the information they need. It provides the following services: ① Security management of network users, including user authentication and access control to prevent unauthorized personnel from obtaining information; ② Viewing of power grid structure diagrams, categorized browsing and querying of line and electrical equipment parameters, facilitating user understanding of the configuration of operating equipment; ③ Viewing of short-circuit currents and branch current lists under various fault conditions at different points in the power grid diagram, giving users a direct understanding of the power grid's operation; ④ Browsing of protection configuration information and protection settings for various switches and components in the power grid diagram. Users can select devices in the browser to display the protection configuration and setting parameters of those devices; ⑤ Functions such as searching, browsing, and downloading protection setting sheets and setting calculation sheets. Users can perform queries based on protection type, protected equipment, and other conditions. 5 Conclusion This paper introduces a multi-voltage level power grid relay protection setting and information management system combined with the Web. This system is comprehensive, easy to operate, intuitive, and efficient. It can meet the needs of power system relay protection work and can also serve as part of modern power system relay protection integrated management. The system has been successfully applied to relevant power supply companies under the Shanghai and Zhejiang power grids, achieving good application results.